Usual stuff about the recommended way to make changes to themes is via a Child Theme.
Site name:
Currently, the font list is:
#header h1 {
font-family: Arial,Helvetica,Sans-serif;
...
}
Add a new rule specifying whatever font list you want (in your child theme's style sheet, if you have one). Remember to end the font-list with a generic font.
It's also worth remembering that you cannot guarantee what fonts will be installed on a user's machine, so you should make sure you include in the list acceptable fonts that you can be pretty sure are available at least for Windows and Mac boxes (and I'd include Linux boxes as well).
If you want, you can use Google fonts, of course. There's a plugin for it:
http://wordpress.org/extend/plugins/wp-google-fonts/
Don't know how good it is as I've never used it.
Make the ECO part of the title green:
I can't think of any way you can do this without hard-coding the site title rather than getting it from the WP settings for your site.
If you don't mind doing that, you need to (copy your header.php file from your parent theme directory to your child theme directory and then in the child theme version) alter the line of code that outputs the site title. You'll need to surround the ECO part of the title with a <span> element that contains an id so that you can then add a style rule for it in (your child theme's) style.css.
HTH
PAE